Plotter for navigational flight planning



Sept. 13, 1960 I. GRINGORTEN PLOTTER FOR NAVIGATIONAL FLIGHT PLANNING 2 Sheets-Sheet 1 Filed June 10 w H I. n G 3 INVENTOR GRINGQRTEN BY WW IRVING Sept. 13, 1960 l. GRINGORTEN 2,952,074

PLOTTER FOR NAVIGATIONAL FLIGHT PLANNING Flled June 10, 1958 2 Sheets-Sheet 2 QEBwmOmO N h A n. $555 @222 vol EDOI .562 O e OON O OOw Q OON Q INVENTOR, GRINGORTEN IRVING I. By WW A TTQRNEYSN e 2,952,074 lc Patented Sept. 13, 1960 atent Fig. 3 illustrates how heading and groundspeed are determined, given course, airspeed and D-field or wind 2,952,074 compondentls;

Fig. s ows how course and groundspeed are deter- PLOTTER Ag& FLIGHT 5 mined, given airspeed, heading and D-field or wind components; Irving [.Gringorten, 14 Sheflield Road, Natick, Mass. ig. 5 illustrates estimation of yi time less thanone our; Flled June 1958 741,200 Fig. 6 illustrates estimation of flying time in excess of '4 Claims. (Cl. 33-1 10 (mellow; and

Fig. 7 shows how groundspeed is determined (hourly (Granted 11111161 Title Code ground distance), given two check points and flying time between them.

Referring now to Fig. 1, there is shown a preferred The invention described herein may be manufactured 15 embodiment of the invention and since it is readily usable and used by or for the United States Government for with a 4-dimensional analysis of winds (in horizontal, governmental purposes without payment to me of any vertical, and in time), the invention may be properly royalty thereon. called a 4-D plotter. The plotter itself 13 is constructed This invention relates to aplotter or computer which infrom a single piece of thin, transparent plastic material cludes a flat transparent piece of plastic material or for a given chart projection. In the embodiment shown, Plexiglas marked with lines, graphs, compass rose and slits the 4D plotter is assumed to be made for the Lambertand designed to speed up long-range flight planning Withconformal chart, scale l:l0,000,000, with standard out loss of accuracy. More particularly, the invention is parallels at 30 and 60. concerned with providing a tool which is useful in speed- In the lower third of the plotter are scales NM and NM ing up the plotting of flight plans while taking into conwhich indicate map distances versus latitude, much like sideration the speed and direction of the aircraft as the scale of distances in nautical miles of any map projecwell as the speed and direction of the prevailing winds tion of the earth. The distances are measured from the which normally affect the flight pattern of the aircraft. central vertical line Y'OY, both to the right and to the The task of flight planning becomes significantly great left. For example, if the airspeed of an aircraft is 300 wherever there is a multiple operation of aircraft whose knots at latitude 20 N. the plotter shows that the airspeeds and altitudes of flight differ widely. Basically, the speed would be 317 chart-knots. The expression chartaim of flight control operation is to obtain substantially knots is used to designate the distance on the chart meas complete coordination of effort among the weather foreured with a standard 1:l0,000,000 scale. caster, flight planner, dispatcher and navigator. Thus, it The scales G and G in the upper third of the plotter becomes necessary to standardize the system of flight plan 5 are used to convert a contour gradient into terms of a ning in order to reduce flying time by minimal flight geostrophic'wind velocity. The slant lines of the G-scales planning. The present invention is a tool that is particare labelled in feet. If the increase in contour interval ularly useful for this purpose when used with recently or Dvalue of a constant-pressure surface such as 500 developed wind representation charts. millibars per 240 chart miles is, for example, 570 feet at Accordingly, a primary object of the present invention 40 latitude 40 N., the G-graph shows that this is equivalent is to provide a tool for flight planning that is exceptionally to a geostrophic wind component of 75 chart-knots. By versatile. It is usable for all aircraft speeds between 150 looking down to the NM scale, this wind component is knots and 500 knots, for tailwinds as great as 300 knots seen to be equal to 77 knots at latitude 40 N. and headwinds as great as 200 knots. There will be occasions when a percentage correction Another object of the invention is to provide a plotter should be made to the geostrophic wind approximation. which can be used in flight planning to plot winds either For example, "if tightly packed contour lines are curved, on a constant-pressure chart or on a chart of streamlines as around a trough or cyclone, the actual wind will be and isotachs. Weaker than the geostrophic wind. Suppose a 30% cor- A further object of the invention is to provide a means rection is desired to an initially given wind of 77 knots for expediting the overall task of single-heading flight at latitude 40 N., entered in the G-scale at g. Then the planning, flight planning along great circles and rhumb 30% correction is obtained by visually following a line lines or any other fixed track, as well as minimal flight parallel to YOY' till the line marked 45 is reached. planning. This is the zero line. Then a direction is followed, using As mentioned above, the extraordinary Versatility of the slant lines as guides down to the line marked 30%. the invention makes it useful as a substitute for elaborate This gives a corrected velocity of 55 knots at latitude computers which are presently used for flight planning 40 N. purposes. The user of the invention is capable of When the chart distance between two points on the determining the hourly air travel of an aircraft when the map is not 240 nautical miles, it is still possible to find airspeed and latitude positions are known. Also, the the geostrophic wind component from the D-gradient. plotter is useful for converting a contour gradient on a For example, if the chart'distance between two points on weather map into terms of a geostrophic wind velocity. a map is 300 nautical miles the 300-tick in the P-scale or Many other features and advantages of the invention the P'-scale is joined by a line to the central point 0 of the and its operation as a plotter for rapidly making various plotter. If the difference in D-values between two points navigational determinations necessary for proper flight is 580 feet at latitude 40 N., the G-graph is entered at planning, will become more apparent from the following point g, and a line is visually followed parallel to YOY description taken in connection with the illustrative embodiments in the accompanying drawings, wherein:

Fig. 1 is a view of the 4-D plotter showing the compass rose as well as the lines and graphs which are necessary for operating the plotter;

Fig. 2 illustrates a change in tailwind velocity during one hour of flight;

to intersect the slant line OP at t or OP at t. The line from 1 parallel to XOX is followed to intersect the central vertical line at c. The procedure yields 00, a wind component of 60 chart-knots or 63 knots at latitude 40 N. l The C-scale, in the upper left hand portion of the plotter, is a special scale that can be used in the case when the airspeed of the aircraft is 425 knots.

. forward until stopped by the pencil at Q.

- component.

The upper right-hand corner of the plotter is bounded bytwo straight lines, while the remainder of the periphery consists of a. French curve that can be used for the drawing of time fronts. Also included on the lefthand side of the plotter are a group of geometric cutouts which may be. used as templates for the drawing of small triangles, circles or squares; A number of slits are included in the plotter whose purposes will be explained later. One of these slits is provided with an extra notch at position 0,

Some of the operations for which the 4-D plotter may be used, will now be described in detail. One of the first considerations in flight planning is the direction and velocity of the wind at flight level. Below are, several determinations which can be madeby use of the 4-D plotter. I

Suppose the aircrafts position is located on aweather chart that has D-lines or contour intervals on it. .Let the airspeed be 300 knots, latitude 40 N. Find the point E on the plotter by meansof the NM-scale and place it over the aircrafts position with the line EO along the aircrafts heading. Thedistance- EO gives the hourly air motion ofthe aircraft. The next problem is to find the tailwind using the .D-gradient. The two lines on the plotter, as and fw, havebeen placed 240 nautical m-ilm apart with the line XOX exactly. in be tween them. Approximately midway between E and O read the D-values at the ends of a line crossing the heading, as at q and q. If the D-value at q is: less than that at q there is a tail-wind; if the D-value is greater at q than at q there is a headwind. For a tailwind, enter the dif-, fercnce of D-values in the G-scale. Suppose this entry is at g. Visually follow a line parallel to YOY' down to the:

on a weather chart, place the plotterover the map with the pencil point inserted in the slit Q'Q and on top of the aircrafts/ position on the map. Move the plotter Place the line Q'Q in the direction of the aircrafts heading. Read the difference of D-values across the heading of the aircraft and enter this difference into the C-scaler Make use of one of the slits YY andZZ to enter thepencil point and push the plotter forward (or back) until stopped by the pencil along line bb. The point Owill then be on the nexthourly position of the aircraft corrected for tailwind.

The above method of finding the tailwind component presupposes that the effective tailwind can be determined by the D-gradient at approximately the mid-point of each hourly leg of the flight. But there may be considerable change in the tailwind component from the first half-hour l of a flight tothe second half-hour of flight as shown in Fig. 2. In such a case, the D-gradient can be measured scale of the chart.

the airspeed"isSOOiknotS, the crosswindshouldbe aver- .aged over the .300 nautical mile motion. This is accom- I plished by first finding the point E on the plotter a dis-' 7 tance of 300 miles from point 0, measured with the basic Then, draw on the plotter the two slant lines between point 0 and the 300 nautical mile ticks in the P and Pscales.

the difference of D-values from E to 0. If the D-value atE is greater than the D-value at 0, then there will be a right-drift. Enter the difference in value of D, say

' 570 feet, into the G-scale. Follow the guide lines parallel i The lines OP and OP should be drawn on the plotter for I line OE lines along the line p p flight plan except possibly that airspeed, and the plotter used this way for the whole last hour of glide.

When the geostrophic approximation to the wind is not readily availableand the forecaster finds it best togive the wind indirect terms of direction and speed, then the plotter can be used by selecting the point E corresponding to the airspeed, as determined on the NM scale, If the airspeed is 309 knots at latitude 40 N. thenthe distance E0 is equal to 291 nautical miles measured with the 1:10,000,000 scale. aircrafts heading; Placing the pencil point at O, rotate point at the wind speed corrected for latitude.

position of the aircraft.

To find the heading and groundspeed in the determination of the hourly motion along a fixed path or course,

where, the course. is given by two points on a map, 12 and p Fig. 3, place the plotter with point 0 on top of the point p of the map. Rotate the plotter until the i Let distance OE be equal to the airspeed. Obtain the D-gradient across the wind or ss for headwind, and slide the plotter forward axis of the aircraft, that is, the difference of the D-values at q and q. Enter this value in the G-scale'for tailwind or in the G-scale for headwind. Use the slit W for tailguidelines parallel to XOX and plot the crosswind added mechanically to give the etfective hourly tailwind a The effect of-the crosswlnd should be determined over the full hourly motion'O1 theal GI L For example," if

tance mp gives the groundspeed. To find the drift angle,

keep thepencil point on p and slide the plotter forward until stopped'by the pencil point at Q, the center of the 1 protractor.

The reading of the line p p on' the smaller protractor scale n, n, or n (Fig. 1) gives the drift angle.

When it is desired to find the hourly motion including the'co'urse and groundspeed having given the heading, the procedure as outlined above for determining the tailwind (or headwind) is first followed which gives the forward motion from the point p on the chart to. the point p g as shown in Fig. 4. Next the. eifect of the crosswind is.

determined which gives the drift from p to p The direction of the line mp gives the course and .its length gives the groundspeed.

The estimation." of iiyingtime between check points is llustrated in Fig 5 and 6. In estimating flying times of Place the line E0 on the 4D chart in the direction of the aircrafts heading, read.

for the first hour of climb and Set E0 in the direction of the l less than one hour (Fig. 5), p and p are positions on a chart one hour apart. To find the flying time from p to place a pencil point through slit ww on point p of the chart. Slide the plotter till the point w of the plotter is on top of point p; of the chart. Rotate the plotter till the line (or slit) ss falls on top of point p Since the lines paralleling OX divide the rectangle between as and wf into 12 equal slices, each slice represents five (5) minutes. This makes it possible to estimate the fraction of one hour of flying time from p to p to the nearest minute. In Fig. 5 this gives the flying time from p to as 42 minutes. The lines above ss' have the same spacing as the lines below as. This makes possible estimation of flying time greater than one hour. For example, in Fig. 6 place point w of the plotter over p on the chart. Rotate the plotter until the line (or slit) ss' passes through p Then if the flying time from p to p is one hour, the flying time from p to p can be estimated in excess of one hour. In the example of Fig. 6, the time is one hour and 22 minutes.

The procedure for finding ground speed or hourly distance of travel from two check points is shown in Fig. 7. If the flying time between check points is known, say one hour and 20 minutes, then place point w of the plotter over p and rotate the plotter till the line representing one hour and 20 minutes passes over the point p Through the slit ss mark point p;, on the line p p Then the flying time from p to p is one hour.

The compass rose found on the periphery of the 4-D plotter has its center at point Q which represents a distance of 100 nautical miles from point 0. To obtain directions at a point on a chart, place the pencil through the slit Q'Q on the desired point of the chart. Slide the plotter till the pencil stops the plotter at Q. Rotate the plotter till the line Q'Q parallels the desired direction. If the direction is to be measured relative to true north, then the meridian through point Q will intersect the compass rose to give the directional reading.

The operations described above are useful and necessary for proper flight planning, either on a fixed or predetermined track or on a track that is determined by the flight planning device itself. The plotter is particularly effective in reducing the time necessary to determine the various wind effects on the aircraft and to thereby determine the best flight plan to take advantage of the winds so that the aircraft can reach its destination in the shortest possible time.

Although the 4-D plotter has been described with reference to some of its more particular uses, it can be seen that the present invention comprises a relatively simple and practical navigation device which is eflicient and reliable in use and operation. The device includes only a single piece of flat printed plastic which may be inexpensively produced and is well adapted to accomplish the functions herein set forth, as well as many others.

It will be understood that the description and drawings include only a single preferred embodiment of my invention and that various changes and modifications in the construction, proportion and arrangement of the scales and other portions of the plotter may be made without departing from the true spirit and scope of the invention.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent of the United States is:

1. A navigational course plotting apparatus capable of being superposed on a chart showing contour lines of geophysical conditions, comprising a transparent sheet of material, a graphic representation thereon having ordinate and abscissa markings of distance from a central reference point, said distance markings being measured at a predetermined latitude, a slot along the axis of said abscissa, a slot along said ordinate passing through said central reference point at the intersection of the abscissa and ordinate axes, said ordinate slot including an enlarged portion at said reference point, a series of plots on said graphic representation, one of said plots being located at one end of said ordinate and including a distance versus latitude graph overlaid on said graphic representation for determining chart distance values at various latitudes, a second plot located at the other end of said ordinate and including a graph of latitude versus the altitude difference between contour lines of a constant pressure surface, a pair of spaced slots oriented in the direction of said abscissa, each of said spaced slots extendng outwardly from said ordinate axis, each of said plots and said graphic representation being interrelated such that a chart distance determination made on one of said plots using said graphic representation is transferable to one of said slots by inserting a pencil-like instrument therethrough and contacting the chart therebeneath, said transparent sheet then being movable relative to said underlying chart in the direction of said abscissa until said pencil-like instrument reaches the end of said spaced slot at the ordinate axis of said graphic representation, the new relative positions of said transparent sheet and said chart showing navigational course data.

2. The flight planning apparatus described in claim 1 including a special angular scale disposed near the outer periphery, said angular scale having its axis at the central reference point and being calibrated to represent aircraft speeds at other than normal rates, thereby allowing the device to be used for flight planning when the speed of the aircraft changes during the flight.

3. The flight planning apparatus described in claim 1 including a compass rose disposed on the outer periphery, said compass rose having its center located at the inner end of the slot along the axis of the abscissa and being useful for determining drift angle of the aircraft during flight.

4. The flight planning apparatus described in claim 1 having an irregularly shaped outer periphery, a portion of said periphery being bounded by straight edges at right angles to each other, and another portion being in the form of curved edges, said periphery being useful to draw contour lines and other necessary lines necessary in flight planning procedure.

References Cited in the file of this patent UNITED STATES PATENTS Gottschalk Nov. 7, 

